Sonnax oversized O-ring GM-O-17V can be used to prevent leakage in GM 4L60-E piston/damper assemblies and GM 265mm LU viscous damper assemblies with somewhat worn piston bores.
Be sure to resize the bore of the piston/damper assembly to 1.660" ±.001". In order to avoid the risk of the O-ring coming out of groove, do not exceed this recommended bore specification. If bore wear is too great, [GM-DS-2K] piston/damper sleeve kit can be used to restore the original bore in 4L60-E (300mm) converters.